Engineer Reports Mounting Damage from Big Dig Leaks

Continuing water leaks into Big Dig tunnels in Boston are causing mounting damage to corroding electrical systems and structural steel, among other components, according to an internal report from the Big Dig’s chief engineer, reported on in the Boston Globe.

Chief engineer Helmut Ernst prepared a seven-page report in April with an extensive description of the damage from the leaks, as well as an estimate of repair costs that might total $150 million. Subsequently, the Globe says, the report was condensed to two pages by the Massachusetts highway administrator, Frank DePaola, and softened to indicate the that tunnels are safe and the repair costs are minimal.

Massachusetts Department of Transportation

A portion of The Big Dig project under construction.

Ernst’s report was prepared after a 110-pound light fixture crashed from the ceiling of the tunnel, revealing widespread corrosion in the lights throughout the 7.5 mile-tunnel system.

His report described leak repairs and other remedial work that he estimated would cost $150 million.

He reported that 17 million gallons of water leaking into the tunnel system each year are pumped out, much more than anticipated, resulting in Big Dig’s consistent violation of its state permit for the amount of water it is allowed to pump into the Deer Island Sewage Treatment Plant.

Leaks are causing roadway icing inside the tunnels, which are then treated with deicing salts, exacerbating the corrosion problem, he said.

Ernst also reported widespread corrosion of electrical components and conduit, and initiation of corrosion of structural steel, piling, and girders supporting the tunnel roof.

Part of the ceiling of the Big Dig collapsed in 2006.

Additionally, he reported problems of mold in utility rooms, saturation of fireproofing materials, and damage to the ventilation system.

He also reported the continuation of crack development inside the tunnel due to excessive temperature variations between summer and winter (100 degrees rather than 50) resulting from a design flaw. Major crack repair work is needed, he said in his report.